1. Field of the Invention
The present invention relates to a system to control various kinds of functions of an apparatus to be controlled by electrically exchanging information between the apparatus to be controlled such as a lens unit or the like and a control apparatus such as a camera unit or the like.
2. Related Background Art
In recent years, an exchangeable lens system has also been adopted in a field of, for example, a video camera or the like and the function is remarkably being enhanced. FIG. 1 is a schematic diagram showing an automatic focusing control (hereinafter, referred to as an AF) in, for example, a video camera system of the exchangeable lens system.
In the diagram, reference numeral 1 denotes a camera side and 2 indicates a lens side. The camera side 1 and the lens side 2 are mechanically, optically, and electrically connected by a mount 3 having electrical connection.
A light passes through a focusing lens unit 21, a zooming lens unit 22, and a diaphragm mechanism 23 on the lens 2 side and is converted into a video signal by an image pickup device 11 such as a CCD or the like on the camera 1 side. The video signal is subsequently converted into the composite video signal by an amplifier 12, a signal processing circuit 13, and the like. The composite video signal is supplied to a recording section such as a video tape recorder or the like.
On the other hand, a high frequency component in the video signal which changes in accordance with a focusing state is extracted from the output signal of the signal processing circuit by a filter circuit 14 and is supplied to a camera microcomputer 15 to perform the AF control.
The camera microcomputer 15 calculates a direction signal and a speed signal to drive a focusing lens group on the basis of the level of the high frequency component of the video signal and the present state of the lens such as a depth of field or the like which is obtained by the focusing lens position information (which is detected by a focusing encoder 24 and is obtained through a lens microcomputer 27) in the lens unit 1 and, further, the position information (which is detected by zooming encoder 25 and is obtained through the lens microcomputer 27) and the diaphragm information (which is detected by an iris encoder 26 and is obtained through the lens microcomputer 27) of the zooming lens group. The direction signal and speed signal are transmitted to the lens microcomputer 27 on the lens side through a serial communication line SL.
On the basis of a command from the camera microcomputer 15, the lens microcomputer 27 drives a focusing motor 29 via a motor driver 28, thereby moving the focusing lens unit 21. Information regarding the movement amount in this instance is sent to the camera microcomputer 15 through the lens microcomputer 27 by the focusing encoder 24. The AF control is executed by continuously executing the above series of operations.
The control speed in this instance can be unconditionally determined since the same motor is always controlled in the case where the lens unit and the camera unit are integratedly constructed.
In case of the exchangeable lens system, however, since the lens unit which is connected is changed, the speed of the focusing motor is also changed in accordance with the lens unit attached. Therefore, it is desirable that the focusing speed information which is given from the camera microcomputer 15 to the lens microcomputer 27 has been normalized to a certain form. It is considered that, for example, a change speed of blur circle diameter at the image pickup surface of the image pickup device 11 is used as such normalization information. That is, by controlling so as to set the change speed of the blur circle diameter at the image pickup surface to a predetermined speed even when any lens unit is attached, the AF control can be executed without being influenced by a difference of the characteristics of the lens unit.
Reference numerals 30 and 31 denote a zooming motor and a zooming driver to drive the zooming lens unit 22. The zooming motor and zooming driver are controlled by commands which are generated from the lens microcomputer 27 on the basis of control information from the camera side.
Reference numerals 32 and 33 denote an IG meter and a diaphragm driver to drive the diaphragm mechanism 23. The IG meter and diaphragm driver are controlled by commands which are generated from the lens microcomputer 27 on the basis of control information from the camera side.
On the other hand, FIG. 2 is a schematic diagram showing the AF control in, for example, a silver-salt still camera system of the exchangeable lens system.
In the diagram, reference numeral 4 denotes a camera side; 5 a lens side; and 6 an electrical connection mount. The light passes through a focusing lens unit 51, a zooming lens unit 52, and a diaphragm mechanism 53 on the lens 5 side and is transmitted through a shutter mechanism 41 on the camera 4 side and is formed as an image on a film photo sensitive surface 42.
A sensor unit for AF control (hereinafter, referred to as an AF sensor) 43 is arranged. An output of the AF sensor 43 is supplied through an amplifier 44 to a camera microcomputer 45 to perform the AF control.
The camera microcomputer 45 calculates the movement distance of the focusing lens from the present position of the focusing lens group to the in-focus point on the basis of an output signal of the AF sensor 43 and the present state of the lens due to the position information (which is detected by a zooming encoder 54 and is obtained through a lens microcomputer 59) of the zoom lens group of the lens unit 5, the diaphragm information (an opening F-No that is inherent to the lens unit and is obtained through the lens microcomputer 59), and the like. The camera microcomputer 45 subsequently supplies a direction signal and a signal indicative of the number of drive pulses to drive a pulse motor on the lens side to the lens microcomputer 59 through the serial communication line.
The lens microcomputer 59 drives a focusing motor 55 via a motor driver 56 on the basis of a command from the camera microcomputer 45, thereby moving the focusing lens unit 51 to the in-focus point. The AF control is executed by the above series of operations.
The number of pulses to control in this instance can be unconditionally determined because the same motor is always controlled in the case where the lens unit and the camera unit are integratedly constructed.
In case of the exchangeable lens system, however, since the lens which is connected is changed, a focusing change amount per pulse is also obviously changed in accordance with the lens unit attached.
Therefore, it is desirable to construct the camera side in a manner such as to receive information such as lens feed amount per one pulse of the focusing motor, lens sensitivity at the focal distance, and the like from the lens side and to thereby determine the number of drive pulses on the basis of such information.
In the still camera or video movie camera as mentioned above, different from the ordinary camera/lens integrated type system, a plurality of lenses whcih are used for vairous kinds of functions and applications are exchanged and used in accordance with the photographing state, so that a photographing range can be widened, so that an exchangeable lens system is proposed. In such a system the automatic focusing control (AF) and the automatic exposure control (AE) are generally used.
In case of executing such a control as mentioned above, for example, with respect to the AF control the speed control is performed on the basis of the information such as sensitivity, opening F-No, focal distance, and the like of the lens. The information necessary for control on the camera side as mentioned above has ordinarily been stored in an ROM on the lens side. By requesting such data from the camera side to the lens side in accordance with a necessary format and by controlling on the camera side on the basis of the information derived from the lens side, no special problem occurs.
In the case where, for example, the lens for use in the silver-salt still camera which has already existed is also used as an exchangeable lens for use in the video movie camera, however, since a photographing object, a control target, and design idea of the still camera lens are inherently different from those of the exchangeable lens, the data that is needed for processing by the camera side in the exchangeable lens system of the video movie cannot always be obtained from the lens for the still camera in a form as it is. Therefore, it is necessary to convert the data which is obtained from the lens for the still camera into the data of a form that is needed by the processes such as arithmetic operations or the like.
In this instance, however, there is a case where such data is given as a function of the focal distance (data is changed in dependence on the focal distance at the time--the position of a zoom ring). Generally, in case of the still camera, the change in zoom is frequently accomplished by manually rotating the zoom ring by the user by himself. In such a case, the zoom ring cannot be rotated from the camera side.
Therefore, there is considered to use a method whereby in order to enable good AF control and AE control to be executed from the beginning, peculiar data that is necessary for the AF control and AE control of various lenses are previously stored into a memory device and means for recognizing the type of lens attached in the case where the lens was attached and means for reading out the data of the lens recognized from the memory device are provided.
In the above conventional apparatuses, however, when the data to be stored has some inconveniences, for example, when the data abnormally changes due to an erroneous fetching of the data in the attaching/detaching operations of the lens or the like, so long as the maximum or minimum value of the changed data is needed to control, the data is stored into the memory device at a time point when the abnormally changed data becomes the maximum or minimum value. Not only the normal control is not executed but also such a situation becomes a cause of the abnormal operation, so that it is extremely unpreferable.